Drain Electrical Devices, Methods, and Systems

ABSTRACT

A peristaltic pump that reduces electrical current flowing through a pumping tube segment includes a central rotor mounted on a central rotation axis, a shoe with a curved surface facing toward the central rotor, multiple rollers mounted along the circumference of the central rotor and the pumping tube segment positioned between the curved surface and the central rotor. Each roller of the plurality of rollers is a member of a roller group, each roller group includes at least two rollers, rollers in a particular roller group are physically located closer to each other than to rollers in other roller groups, and at least two rollers pinch a portion of the pumping tube segment against the curved surface through a full rotation of the central rotor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 63/216,725 filed Jun. 30, 2021, which is incorporated herein by reference in its entirety.

BACKGROUND

The use of electrically powered medical devices or equipment connected to a patient is very common in modern medicine. Along with the benefits these devices are designed to bring to a patient, they also can create a potential hazard of electric shock to the patient. Electric shock can be caused by current (referred to as leakage current) flowing through the patient, for instance, creating problems such as ventricular defibrillation in the patient's heart, which a medical device may induce in patient at ground potential or sink to ground if the patient is in contact with another source of electricity. It is desirable to design medical equipment to reduce leakage current. In particular, it is desirable to provide a pump that reduces or entirely blocks the passage of leakage current through the pump.

SUMMARY

In certain embodiments, a leakage current path may be formed in a fluid line, such as a drain line. Often, fluid is pumped through a fluid line using a pump, such as a peristaltic pump. A peristaltic pump includes a rotor around which a plurality of rollers is disposed, and the rollers come into contact with a piece of compliant tubing and press it against a part referred to as a pump shoe. A peristaltic pump according to embodiments of the disclosure, reduces or entirely blocks and prevents the flow of leakage current through the pipe which is serving as the pumping tube segment, by ensuring that conductive fluid in the pumping tube segment is forced out of certain areas and thereby interrupting a conductive pathway through the pumping tube segment.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate exemplary embodiments of the disclosure, and, together with the general description given above and the detailed description given below, serve to explain the features of embodiments of the disclosed subject matter. The accompanying drawings have not necessarily been drawn to scale. Where applicable, some features may not be illustrated to assist in the description of underlying features.

FIGS. 1A and 1B illustrate a peristaltic pump according to embodiments of the disclosure.

FIG. 1C illustrates various dimensions of a peristaltic pump according to embodiments of the disclosed subject matter.

FIGS. 2A and 2B illustrate a peristaltic pump according to further embodiments of the disclosed subject matter.

FIGS. 3A and 3B illustrate a peristaltic pump with a pump shoe according to embodiments of the disclosed subject matter.

FIGS. 4A-4C illustrate a peristaltic pump with a pump shoe and pressing cones according to embodiments of the disclosed subject matter.

FIG. 5 illustrates a peristaltic pump with a larger pump shoe according to embodiments of the disclosed subject matter.

FIG. 6 illustrates a process flow for controlling peristaltic pump according to embodiments of the disclosed subject matter.

DETAILED DESCRIPTION

Embodiments will hereinafter be described in detail below with reference to the accompanying drawings, wherein like reference numerals represent like elements.

Referring now to FIG. 1A, a peristaltic pump 100 is shown. In a typical peristaltic pump, a rotor 120 carries a number of circumferential rollers (101, 102, 103, 104), possibly mounted on bearings, each of which is arranged to compress a flexible tube 130. As the rotor rotates, a part of the tube is compressed by a roller, thus occluding the tube and forcing the fluid to move through the tube in the direction of movement of the roller. The tube is fabricated from a resilient material and thus reassumes its normal cross-sectional profile after the compression by the roller ceases. This process of peristalsis mimics many biological systems (such as the action of esophagus or the gastrointestinal tract). A body of fluid (or bolus) trapped between two successive rollers is thus transported at ambient pressure toward the pump outlet.

The peristaltic pump 100 includes a rotor 120 mounted on and rotatable about a central point or axis 121, and positioned in close proximity to a pumping shoe 125. As indicated by the double-sided arrow in FIG. 1A, the rotor 120 and the shoe 125 can be moved relative to each other such that the gap between the rotor 120 and the shoe 125 can be increased or decreased. The shoe 125, the rotor 120, or both may be installed on a shaft or rod 114 that is inserted in a spring 116 or other biasing mechanisms which urges the rotor and the shoe against each other, as shown in FIG. 1A. It will be understood that the central axis 121 of the rotor 120 can also be biased in addition to the shoe 125, or be biased instead of the shoe 125 with a biasing mechanism, such as a spring, an electro-magnet, a linear motor, or a hydraulic piston, and other mechanisms that can apply a force or a torque on the axis 121.

The central rotor 120 includes multiple pumping rollers installed around its outer circumference. In the embodiment of FIG. 1A, individual pumping rollers 101, 102, 103, and 104 are shown, but fewer or more rollers may be present, as described in other embodiments of the present disclosure. In an embodiment, the rollers 101, 102, 103, and 104 are spaced at equal angular spacing around the circumference of the rotor 120. Each of the rollers is mounted on its own axis which allows the roller to rotate. In an embodiment, each of the multiple axes of the rollers is positioned on the outer circumference of the rotor 120. In other embodiments, the central axes are positioned closer to the central point 121 such that they are not positioned on the outer circumference. FIG. 1A illustrates the entire circumference of each roller to aid in the understanding, but it will be understood that normally the entire circumference of the individual or rollers would not be visible as it would be covered by a portion of the rotor 120. Thus, FIG. 1A can be thought of as a schematic representation, or a partial cut-away that shows the rollers without obstructions.

The rotor 120 rotates in the clockwise direction in FIG. 1A, as indicated by the dashed arrow to cause the peristaltic pump to pump fluid through a pumping tube segment. A length of compliant hollow tube is positioned in the space between the rotor 120 and the shoe 125. This part of a hollow tube is referred to as a pumping tube 130 or a pumping tube segment 130. When the pumping tube segment 130 is so positioned, when the central rotor 120 rotates, the individual pumping rollers 101, 102, 103, and 104 are pressed against the pumping tube segment 130 at pinch point 135 as shown in the figure. As shown in FIG. 1A, there are two pinch points 135 created by rollers 102 and 103 when the rotor 120 is at the particular angular position shown. At each pinch point, the walls of the pumping tube collapse such that all fluid is pressed out of the tube at that location. The pinch point migrates along the curved surface 145 of the shoe 125 and thereby urges fluid ahead of the pinch point to move in the rotation direction of the rotor 120.

The capital letter A represents the angular spacing of rotors along the central rotor 120. In the example of FIG. 1A, the angular spacing is 90 degrees because the four rollers illustrated in FIG. 1A are spaced equally around the outer circumference of central rotor 120. As noted above, there can be more or fewer than four rollers. In embodiments, the angular spacing is 120 degrees.

The pumping tube segment 130 may be filled with a fluid which can conduct electricity along the length of the pumping tube segment. In an embodiment, the pumping tube segment is fluidly connected to or a part of a drain line of a peristaltic dialysis system. In this situation, dialysate will at times flow through the pumping tube segment 130. In embodiments, the pumping tube segment is fluidly connected inline with a drain line in a peritoneal dialysis system, conveying waste dialysate from a patient (peritoneal cavity) to a drain. The drain may be at ground potential. This creates a risk of leakage current flowing through the dialysate and the pumping tube segment 130 to ground.

Continuous occlusion of the pumping tube segment 130 prevents electrical current from flowing through the pumping tube segment 130. To reduce the chance of leakage current flowing through the drain line, a pinch point 135 is maintained at all times to maintain an area that is devoid of the conductive fluid in the pumping tube segment 130. This is illustrated in FIG. 1B.

Referring to FIG. 1B, the central rotor 120 has rotated by approximately 45°, and it can be seen that in this situation, pumping roller 102 remains pressed against pumping tube segment 130 at the pinch point 135, while pumping roller 103 is no longer in contact with the pumping tube segment 130. In this situation, only a single pinch point 135 is created for at least a portion of the peristaltic pumping cycle. To ensure that no conductive fluid is present at the pinch point 135 the spacing between the central rotor 120 and the shoe 125 can be adjusted such that a sufficient force is applied by the rollers against the pumping tube segment 130 whenever a roller is in contact with the pumping tube segment. Further, the pumping tube segment size and material durometer, roller diameter and width, length and curvature of surface 145 are selected to ensure that complete occlusion occurs at the pinch point 135.

In some circumstances, due to deterioration of the material of the pumping tube segment 130, the wear of the rollers, and/or wear of the shoe, it may be desirable to ensure that at least two pinch points 135 are created at all times. This is because there is a possibility that the single pinch point may be insufficient to completely force all conductive fluid from the pinch point, thus leaving open the possibility that some electrical current may pass through the pumping tube segment 130. Ensuring that two pinch points are always present reduces the likelihood of leakage current flowing through the pumping tube segment.

Turning to FIG. 1C, peristaltic pump 100, as shown in FIG. 1B, is shown. The angular spacing of the rollers is the same as shown in FIG. 1A. In addition, the length of the curve the surface 145 of the shoe 125 is represented by capital letter L. The length L is the length measured around the curvature of the surface. Further, as shown by the Greek letter α, the curved surface of shoe 125 has an angular extent. There is a correlation between the angular extent α and the length L as will be understood. When the curvature of the curved surface is a part of a circle, the length L can be determined as a part of a circumference of that circle. Even when the curved surface does not have a curvature of a circle, but instead of an ellipse or some other ellipsoid, the angular extent α is related to the angular distribution of the rollers along the rotor 120. In embodiments, the angular extent α is sufficiently large to guarantee that two rollers are always positioned radially against the curved surface such that two pinch points 135 are provided when a pumping tube segment is inserted into the space between the rotor 120 and the shoe 125. In embodiments, when the angular spacing of the rollers is A degrees (FIG. 1A), the angular extent a is greater than or equal to 2×A degrees, which guarantees that two pinch points 135 will always be present when the rotor 120 rotates through 360 degrees. Thus, providing more rollers (and thus decreasing A) can be used to ensure two pinch points 135 when the angular extent α needs to be small (due to other design constraints). Conversely, the angular extent α of the shoe curved surface can be selected to ensure at least two pinch points 135 when the number of rollers is constrained.

In embodiments, a peristaltic pump 100 reduces or eliminates electrical current flow in the pumping tube segment 130 by coupling a rotor with rollers that are separated from adjacent rollers by A degrees with a pump shoe that has an angular extent α greater than or equal to 2×A degrees.

Referring to FIG. 2A, an embodiment of a peristaltic pump 200 which ensures that at least two pinch points (but possibly more) are created at all times is shown. for increased clarity, the pumping tube segment 130 is omitted from FIG. 2A, but it will be understood that the pumping tube segment 130 would be installed much as in FIG. 1A.

Peristaltic pump 200 includes a central rotor 220 which has multiple rollers disposed around its outer circumference. The multiple rollers are grouped into roller groups. In an embodiment, as illustrated in FIG. 2A, four roller groups are present. Each of the four roller groups has two rollers. Rollers 201 and 202 are members of a first roller group; rollers 203 and 204 are members of a second roller group; rollers 205 and 206 are members of a third roller group; and rollers 207 and 208 are members of a fourth roller group.

Although four roller groups are illustrated in FIG. 2A, it will be understood that there may be more or fewer roller groups present, and that each roller group may have more than two rollers in it. The specific number of roller groups and rollers within each group is dictated by the size of the rotor 220 and the length of the surface 145 of the shoe 125. In embodiments, the number of roller groups, number of rollers per roller group, and the length of the surface 145 are selected such that at all times there are two or more pinch points 135 along the pumping tube segment 130. When referring to the length of the surface 145 of the pumping shoe 25, it is the length L along the curved surface 145 which mates with the pumping tube segment that is referenced.

As shown in FIG. 2A, the spacing of all rollers along the circumference of the rotor 220 is not uniform, but instead rollers in a roller group are closer to other rollers in that group. For example, in an embodiment there are four roller groups, each roller group separated from the adjacent roller group by 90 degrees (similar to the arrangement in FIG. 1A). More specifically, the middle of each roller group is 90 degrees from the middle of an adjacent roller group, even if individual rollers in one group may be less than 90 degrees spaced from rollers in another roller group.

In embodiments, there are four roller groups on rotor 220 and each roller group includes two rollers which are closer to each other then they are to rollers in other roller groups. In such embodiments, at least 2 rollers included in one or more of the roller groups pinch respective portions of the pumping tube segment 130 against the curved surface through a full rotation of the rotor 220. In other embodiments, there are four roller groups and each roller group includes three rollers. In further embodiments, there are three roller groups and each roller group includes two rollers, three rollers, or four rollers.

When more than two pinch points 135 are present at all times, it is possible to ensure that no electrical current can flow through the pumping tube segment 130, even if a conductive fluid is being pumped through the pumping tube segment 130. In an embodiment, there are three rollers in each roller group, as illustrated in FIG. 2B.

Referring now to FIG. 2B, a peristaltic pump 290 is shown. The pump 290 includes a rotor 320 which has on it multiple roller groups. Roller group 321 is indicated in the figure, and includes separate rollers 301, 302, and 303. The pump illustrated in the embodiment of FIG. 2B includes four roller groups, but fewer or more roller groups can be present. In an embodiment, the rotor 320 includes four roller groups, and each roller group includes three rollers. More specifically, rollers 304, 305, and 306 are members of a roller group; rollers 307, 308, and 309 are members of another roller group; and rollers 310, 311, and 312 are members of yet another roller group. Advantageously, this arrangement guarantees that there will always be at least 3 points of a contact (pinch points 135) on the pumping tube segment 130 (which is not illustrated in FIG. 2B for clarity). For example, in the embodiment of FIG. 2B, at least 3 rollers included in one or more of the roller groups pinch respective portions of the pumping tube segment 130 against the curved surface through a full rotation of the rotor 320.

FIG. 3A illustrates peristaltic pump 300 which includes a rotor 120 with rollers 101, 102, 103, and 104. The peristaltic pump 300 in this embodiment includes a modified shoe 325, as shown. The modified shoe 325 has a curved surface 345 which faces toward the rotor 120. The modified shoe 325 may be biased by spring 116 along biasing a rod 114, or other urging mechanism, similarly, to pump 100 in FIG. 1A. The curved surface 345 of modified shoe 325 includes a protrusion 335. The protrusion 335 is a discontinuity in the curvature of the curved surface 345 and has the effect of creating a pressure spike when any of the rollers rolls over the protrusion. By providing a protrusion such as 335 along the curved surface 345, the occlusion of the tube 130 (not illustrated to increase clarity) is increased. By providing a pressure spike at a particular location, the likelihood that any conductive fluid remains in the occluded portion of tube 130 is reduced, thus reducing the possibility of a leakage current flowing through pumping tube segment 130.

As shown in FIG. 3B, pumping shoe 326 may include more than one protrusion 335. In an embodiment, two protrusions 335 are present along the curved surface 346. In other embodiments, three protrusions 335 (not illustrated) are present, and spaced with an equal distribution along the curved surface 346. In embodiments, the rotor includes three rollers, four rollers, five rollers, six rollers, seven rollers, or eight rollers. It will be understood that the pump shoe 325 and 326, with one or more protrusions 335 can be used with any of the rotors described in the present disclosure.

FIG. 4A illustrates an embodiment of pump shoe 427 with a plunger 420 protruding through an opening 450 in the curved surface 447. The plunger 420 can be a curved plunger, as illustrated, mounted on a movable platform such as a rod biased with a spring 416. In embodiments, the spring can be omitted or substituted with a hydraulically actuated plunger which can move the leading tip, or edge, of plunger 420 in and out of the surface 447. The view shown in FIG. 4A can be thought of as a cross sectional view as the top of plunger 420 protrudes through an opening 450 in the surface 447. The tip may have a conical cross-section as shown. It is envisioned that pump shoe 427, and all other pump shoes disclosed herein, may be used with any of the pump rotors described in the present disclosure. For example, pump rotor 120 may be used with pump shoe 427. In an embodiment, the conical tip of plunger 420 protrudes from the middle of the curved surface 447 of pump shoe 427.

In other embodiments, as shown in FIG. 4B, the plunger 420 is positioned at a location that is not in the middle of the curved surface 448 of shoe 428, but instead closer to one end of the surface. The opening 450 is not expressly illustrated, but it is understood that the plunger extends out of an opening, much like in FIG. 4A. This arrangement may increase pumping efficiency (volume per number of rotor rotations).

In yet other embodiments, multiple plungers 420 may be used, as illustrated in FIG. 4C. Two plungers 420 are positioned toward two ends of the curved surface 449 of pump shoe 429. It will be understood that the plungers 420 generate an increased pressure at a pinch point formed between a roller and the plunger, thereby reducing the possibility of a conductive fluid being retained at the pinch point inside of pumping tube segment 130. Thus, an electrical current cannot flow through the pumping tube segment 130.

Referring now to FIG. 5 , a peristaltic pump 500 includes a central rotor 520, which is not necessarily circular in shape. In embodiments, the central rotor may have a substantial triangular shape, or a star shape. The central rotor shape illustrated and described here can be used with any of the other peristaltic pumps described in this disclosure, and the term rotor does not necessarily require a circular shape. The rotor 520 has three rollers 501, 502, and 503. The rotor 520 is positioned against pump shoe 525 which has a curved surface 545 that has a length indicated by the dashed line at 546. The length of the curved surface 545 of the shoe 525 is greater than the length of the other curved surfaces shown in the other figures. Thus, the goal of ensuring that two rollers are always in contact with a pumping tube segment 130 (which is not illustrated in FIG. 5 for increased clarity) can be maintained with fewer than four rollers on a rotor, by extending the length of the curved surface of the pump shoe.

In embodiments, a peristaltic pump includes a rotor with three rollers mounted on the outer circumference of the rotor, and a pump shoe which has a curved surface which presses against the rollers and has a length that is sufficient to ensure that at least two of the rollers are always in contact with the curved surface during operation of the pump.

FIG. 6 illustrates a process for reducing or blocking electrical leakage current in a pumping tube segment 130 using a peristaltic pump according to any of the disclosed embodiments. In addition, or instead of, the structural features described above that reduce or eliminate the leakage current in the pumping tube segment, it is possible to operate a peristaltic pump according to the process illustrated in FIG. 6 to further reduce or eliminate leakage current. At S610 the pump rotor rotates forward (in the normal direction) to cause fluid to be pumped through the pumping tube segment. While the pump is operating, an electrical current sensor (not illustrated) is provided to detect electrical current flowing through the pumping tube segment 130. If the electrical current sensor detects a current above a predetermined threshold (such as 50 μA) at S620, the process continues at S630. On the other hand, if no electrical current is detected, the pump rotor operates normally.

At S630, the peristaltic pump is controlled to block the flow of current. According to embodiments, the peristaltic pump rotor continues rotating forward until two rollers are in contact with the pumping tube segment and pressing against the pumping shoe, thus ensuring that are two pinch points exist.

In other embodiments, when electrical current is detected, the pump rotor is reversed and rotates in the opposite direction, until rollers come to rest at a position that creates two pinch points.

In other embodiments, the peristaltic pump rotor is stopped and the pressure between the roller that is in contact with the pumping tube segment and the pump shoe is increased. In embodiments, the rotor may rotate forward or backwards until one roller stops at a position that maximizes the pressure on the pumping tube segment. For example, this position may be substantially horizontal in FIG. 5 such that roller 502 would be pressing into the middle of surface 545. In this situation, if pump shoe 525 is mounted on a pressure biasing mechanism similar to that shown in FIG. 1A, the pressure from that mechanism acts directly against the roller 502, thus maximizing the pressure on the pumping tube segment at that location, thereby minimizing the possibility of a conductive fluid being present at that location of the pumping tube segment.

In embodiments, this increase in pressure can be achieved by increasing the spring tension of a biasing spring such as spring 116 described above. In other embodiments, the pressure can be increased with a pressure mechanism such as those described above, which presses the rotor and/or the pump shoe against each other with a pressure that is greater than the normal operating pressure. Thus, the pinch point that is maintained at this state is under a greater pressure than a normal operating pressure, thus reducing the possibility of fluid being present in the pumping tube segment at the pinch point.

In further embodiments, S630 includes stopping the rotation of the rotor which is initially rotating in the forward, rotating the rotor in the reverse direction for several degrees of rotation (e.g., 5, 10, 15, 20, 25 degrees), and then again rotating in the forward direction. This action forces out fluid that may be at the pinch point through a squeegee action, without the need for increasing the pressure at the pinch point. Of course, this operation can be combined with the other disclosed embodiments. For example, the forward and backward rocking of the rotor can take place with a roller on one of the protrusions 335 of the pump shoe, to further enhance the squeegee effect and force out fluid from the pumping tube segment 130 at a pinch point.

A medical system, such as one used for renal replacement therapy, may include a dialysis system (hemodialysis, peritoneal dialysis, and others). It is desirable in such a system to eliminate or reduce electrical current flowing in various fluid lines (hollow tubes that convey a fluid, often a conductive fluid). A peristaltic pump according to disclosed embodiments reduces or eliminates such electrical current. One general aspect includes a peristaltic pump that reduces electrical current flowing through a pumping tube segment, and may include a central rotor mounted on a central rotation axis; a shoe with a curved surface facing toward the central rotor; a plurality of rollers mounted along a circumference of the central rotor; and the pumping tube segment positioned between the curved surface and the central rotor, where each roller of the plurality of rollers is a member of a roller group, each roller group may include at least two rollers, rollers in a particular roller group are physically located closer to each other than to rollers in other roller groups; and at least two rollers pinch a portion of the pumping tube segment against the curved surface through a full rotation of the central rotor.

Implementations of the first aspect may include one or more of the following features. The physical location of a roller is determined by a center of the roller. Each roller group may include three rollers.

Another general aspect of the disclosure includes a peristaltic pump that reduces electrical current flowing through a pumping tube segment, and may include a central rotor mounted on a central rotation axis; a shoe with a curved surface facing toward the central rotor and having a length of the curved surface measured along the curved surface in a circumferential direction; and a plurality of rollers mounted along a circumference of the central rotor, where a pumping tube is positioned between the central rotor and the shoe, a pinch point on the pumping tube is defined between any roller pressing radially away from the central rotation axis against the shoe, and a number of the rollers and the length of the curved surface provide at least two pinch points on the pumping tube segment at all times when the central rotor rotates through 360 degrees.

Implementations of this aspect may include one or more of the following features. The at least two pinch points are three pinch points. The plurality of rollers is distributed evenly around the circumference of the central rotor with an angular spacing of A degrees, and an angular extent of the curved surface is greater than or equal to two times A.

Another general aspect includes a peristaltic pump that reduces electrical current flowing through a pumping tube segment, and may include a central rotor mounted on a central rotation axis; a shoe with a curved surface facing toward the central rotor and having a length of the curved surface measured along the curved surface in a circumferential direction; and a plurality of rollers mounted along a circumference of the central rotor, where a pumping tube is positioned between the central rotor and the shoe, a pinch point on the pumping tube is defined between any roller pressing radially away from the central rotation axis against the shoe, and the curved surface of the shoe may include one or more protrusions toward the central rotor, such that pressure on the pumping tube segment between a roller and the protrusion is greater than pressure on the pumping tube segment at any other location.

Implementations of this aspect may include one or more of the following features. The curved surface may include two protrusions that increase the pressure on the pumping tube segment at two different locations. The peristaltic pump may include a biasing mechanism that exerts a force on the shoe in a direction toward the central rotor. The biasing mechanism may include a spring on a rod. The biasing mechanism may include a motor that receives control signals that modulate force applied by the motor to the shoe. The central rotor may be pivotally mounted on a rotation axis, and a biasing mechanism may exert a force on the rotation axis in a direction toward the shoe to press the central rotor toward the curved surface of the shoe. The one or more protrusions may include a movable plunger that extends out of the curved surface of the shoe. The peristaltic pump may include an opening in the curved surface through which the plunger extends out of the curved surface. The plunger may be urged toward the central rotor by a biasing mechanism. The biasing mechanism may include a passive spring. The biasing mechanism may include a motor that is controlled by electrical signals and exerts a force with a magnitude that is based on the electrical signals. The shoe may include two plungers extending from the curved surface at two different locations.

Another general aspect includes a method of pumping a conductive fluid while reducing electrical current flowing through the conductive fluid, and the method may include providing a fluid pump; pumping the conductive fluid with the fluid pump; detecting a presence of the electrical current in the conductive fluid during the pumping; measuring a magnitude of the detected electrical current; comparing the measured magnitude of the electrical current against a predetermined threshold value; and, in response to exceeding the threshold value, modifying the pumping of the fluid pump to reduce the electrical current flowing through the conductive fluid.

Implementations of this aspect may include one or more of the following features. The fluid pump may include a peristaltic pump with a central rotor, a plurality of rollers attached to the central rotor, a pump shoe with a curved surface that is placed adjacent to the central rotor, and a pumping tube segment positioned between the central rotor and the curved surface. The pumping of the conductive fluid may include rotating the central rotor in a first direction. The modifying the pumping of the fluid pump may include stopping the fluid pump in a state where at least two rollers press on a pumping tube segment against a pump shoe. The modifying the pumping of the fluid pump may include rotating the rotor forward or backward until at least one roller is positioned directly against a protrusion on the curved surface of the pump shoe. The modifying the pumping of the fluid pump may include increasing pressure between the rollers and the pump shoe. The increasing the pressure may include using a biasing mechanism to increase a force on a central axis of the rotor in a direction toward the pump shoe. The increasing the pressure may include using a biasing mechanism to increase a force on the pump shoe in a direction toward a central axis of the rotor. The increasing the pressure may include using a first biasing mechanism to increase a force on a central axis of the rotor in a direction toward the pump shoe, and using a second biasing mechanism to increase a force on the pump shoe in a direction toward the central axis of the rotor. The fluid pump may include a peristaltic pump with a central rotor, a plurality of roller groups each including two or more rollers attached to the central rotor, a shoe with a curved surface that is disposed adjacent to the central rotor, and a pumping tube segment positioned between the central rotor and the curved surface, wherein rollers in a same one of the roller groups are physically located closer to each other than to rollers in other ones of the roller groups, and wherein at least two rollers included in one or more of the roller groups pinch respective portions of the pumping tube segment against the curved surface through a full rotation of the central rotor.

According to a first further embodiment, there is provided a peristaltic pump that reduces electrical current flowing through a pumping tube segment, including: a central rotor mounted on a central rotation axis; a shoe with a curved surface facing toward the central rotor; a plurality of rollers mounted along a circumference of the central rotor; and the pumping tube segment positioned between the curved surface and the central rotor, wherein each roller of the plurality of rollers is a member of a roller group, each roller group includes at least two rollers, rollers in a particular roller group are physically located closer to each other than to rollers in other roller groups, and at least two rollers pinch a portion of the pumping tube segment against the curved surface through a full rotation of the central rotor.

According to a second further embodiment, there is provided the peristaltic pump of the first further embodiment or any of the other foregoing embodiments, wherein the physical location of a roller is determined by a center of the roller. According to third further embodiment, there is provided the peristaltic pump of the first further embodiment or any of the other foregoing embodiments, wherein each roller group includes three rollers.

According to a fourth further embodiment, there is provided a peristaltic pump that reduces electrical current flowing through a pumping tube segment, including: a central rotor mounted on a central rotation axis; a shoe with a curved surface facing toward the central rotor and having a length of the curved surface measured along the curved surface in a circumferential direction; and a plurality of rollers mounted along a circumference of the central rotor, wherein a pumping tube is positioned between the central rotor and the shoe, a pinch point on the pumping tube is defined between any roller pressing radially away from the central rotation axis against the shoe, and a number of the rollers and the length of the curved surface provide at least two pinch points on the pumping tube segment at all times when the central rotor rotates through 360 degrees.

According to a fifth further embodiment, there is provided the peristaltic pump of the fourth further embodiment or any of the other foregoing embodiments, wherein the at least two pinch points are three pinch points. According to a sixth further embodiment, there is provided the peristaltic pump of the fourth further embodiment or any of the other foregoing embodiments, wherein the plurality of rollers is distributed evenly around the circumference of the central rotor with an angular spacing of A degrees, and an angular extent of the curved surface is greater than or equal to two times A.

According to a seventh further embodiment, there is provided a peristaltic pump that reduces electrical current flowing through a pumping tube segment, including: a central rotor mounted on a central rotation axis; a shoe with a curved surface facing toward the central rotor and having a length of the curved surface measured along the curved surface in a circumferential direction; and a plurality of rollers mounted along a circumference of the central rotor, wherein a pumping tube is positioned between the central rotor and the shoe, a pinch point on the pumping tube is defined between any roller pressing radially away from the central rotation axis against the shoe, and the curved surface of the shoe includes one or more protrusions toward the central rotor, such that pressure on the pumping tube segment between a roller and the protrusion is greater than pressure on the pumping tube segment at any other location.

According to an eighth further embodiment, there is provided the peristaltic pump of the seventh further embodiment or any of the other foregoing embodiments, wherein the curved surface includes two protrusions that increase the pressure on the pumping tube segment at two different locations. According to a ninth further embodiment, there is provided the peristaltic pump of the seventh further embodiment or any of the other foregoing embodiments, further including a biasing mechanism that exerts a force on the shoe in a direction toward the central rotor. According to a tenth further embodiment, there is provided the peristaltic pump of the ninth further embodiment or any of the other foregoing embodiments, wherein the biasing mechanism includes a spring on a rod. According to an eleventh further embodiment, there is provided the peristaltic pump of the ninth further embodiment or any of the other foregoing embodiments, wherein the biasing mechanism includes a motor that receives control signals that modulate force applied by the motor to the shoe. According to a twelfth further embodiment, there is provided the peristaltic pump of the seventh further embodiment or any of the other foregoing embodiments, wherein the central rotor is pivotally mounted on a rotation axis, and a biasing mechanism exerts a force on the rotation axis in a direction toward the shoe to press the central rotor toward the curved surface of the shoe. According to a thirteenth further embodiment, there is provided the peristaltic pump of the seventh further embodiment or any of the other foregoing embodiments, wherein the one or more protrusions include a movable plunger that extends out of the curved surface of the shoe. According to a fourteenth further embodiment, there is provided the peristaltic pump of the thirteenth further embodiment or any of the other foregoing embodiments, further including: an opening in the curved surface through which the plunger extends out of the curved surface. According to a fifteenth further embodiment, there is provided the peristaltic pump of the thirteenth further embodiment or any of the other foregoing embodiments, wherein the plunger is urged toward the central rotor by a biasing mechanism. According to a sixteenth further embodiment, there is provided the peristaltic pump of the fifteenth further embodiment or any of the other foregoing embodiments, wherein the biasing mechanism includes a passive spring. According to a seventeenth further embodiment, there is provided the peristaltic pump of the thirteenth further embodiment or any of the other foregoing embodiments, wherein the biasing mechanism includes a motor that is controlled by electrical signals and exerts a force with a magnitude that is based on the electrical signals. According to an eighteenth further embodiment, there is provided the peristaltic pump of the thirteenth further embodiment or any of the other foregoing embodiments, wherein the shoe includes two plungers extending from the curved surface at two different locations.

According to a nineteenth further embodiment, there is provided a method of pumping a conductive fluid while reducing electrical current flowing through the conductive fluid, the method including: providing a fluid pump; pumping the conductive fluid with the fluid pump; detecting a presence of the electrical current in the conductive fluid during the pumping; measuring a magnitude of the detected electrical current; comparing the measured magnitude of the electrical current against a predetermined threshold value; and in response to exceeding the threshold value, modifying the pumping of the fluid pump to reduce the electrical current flowing through the conductive fluid.

According to a twentieth further embodiment, there is provided the method of the nineteenth further embodiment or any of the other foregoing embodiments, wherein the fluid pump includes a peristaltic pump with a central rotor, a plurality of rollers attached to the central rotor, a pump shoe with a curved surface that is placed adjacent to the central rotor, and a pumping tube segment positioned between the central rotor and the curved surface. According to a twenty-first further embodiment, there is provided the method of the twentieth further embodiment or any of the other foregoing embodiments, wherein the pumping of the conductive fluid includes rotating the central rotor in a first direction. According to a twenty-second further embodiment, there is provided the method of the nineteenth further embodiment or any of the other foregoing embodiments, wherein the modifying the pumping of the fluid pump includes stopping the fluid pump in a state where at least two rollers press on a pumping tube segment against a pump shoe. According to a twenty-third further embodiment, there is provided the method of the nineteenth further embodiment or any of the other foregoing embodiments, wherein the modifying the pumping of the fluid pump includes rotating the rotor forward or backward until at least one roller is positioned directly against a protrusion on the curved surface of the pump shoe. According to a twenty-fourth further embodiment, there is provided the method of the nineteenth further embodiment or any of the other foregoing embodiments, wherein the modifying the pumping of the fluid pump includes increasing pressure between the rollers and the pump shoe. According to a twenty-fifth further embodiment, there is provided the method of the twenty-fourth further embodiment or any of the other foregoing embodiments, wherein the increasing the pressure includes using a biasing mechanism to increase a force on a central axis of the rotor in a direction toward the pump shoe. According to a twenty-sixth further embodiment, there is provided the method of the twenty-fourth further embodiment or any of the other foregoing embodiments, wherein the increasing the pressure includes using a biasing mechanism to increase a force on the pump shoe in a direction toward a central axis of the rotor. According to a twenty-seventh further embodiment, there is provided the method of the twenty-fourth further embodiment or any of the other foregoing embodiments, wherein the increasing the pressure includes using a first biasing mechanism to increase a force on a central axis of the rotor in a direction toward the pump shoe, and using a second biasing mechanism to increase a force on the pump shoe in a direction toward the central axis of the rotor. According to a twenty-eighth further embodiment, there is provided the method of the nineteenth further embodiment or any of the other foregoing embodiments, wherein the modifying the pumping of the fluid pump includes rotating the rotor forward and backward to squeegee fluid out of a contact pinch point. According to a twenty-ninth further embodiment, there is provided the method of the nineteenth further embodiment or any of the other foregoing embodiments, wherein: the fluid pump includes a peristaltic pump with a central rotor, a plurality of roller groups each including two or more rollers attached to the central rotor, a shoe with a curved surface that is disposed adjacent to the central rotor, and a pumping tube segment positioned between the central rotor and the curved surface; rollers in a same one of the roller groups are physically located closer to each other than to rollers in other ones of the roller groups; and at least two rollers included in one or more of the roller groups pinch respective portions of the pumping tube segment against the curved surface through a full rotation of the central rotor.

Features of the disclosed embodiments may be combined, rearranged, omitted, etc., within the scope of the disclosed subject matter to produce additional embodiments. Furthermore, certain features may sometimes be used to advantage without a corresponding use of other features. It is, thus, apparent that there is provided, in accordance with the present disclosure, a fluid pump and methods for pumping fluid that reduce or eliminate electrical current flowing in fluid pumped by the fluid pump. Many alternatives, modifications, and variations are enabled by the present disclosure. While specific embodiments have been shown and described in detail to illustrate the application of the principles of the disclosure, it will be understood that the disclosed subject matter may be embodied otherwise without departing from such principles. Accordingly, Applicants intend to embrace all such alternatives, modifications, equivalents, and variations that are within the spirit and scope of the present disclosure. 

1. A peristaltic pump that reduces electrical current flowing through a pumping tube segment, comprising: a central rotor mounted on a central rotation axis; a shoe with a curved surface facing toward the central rotor; a plurality of rollers mounted along a circumference of the central rotor; and the pumping tube segment positioned between the curved surface and the central rotor, wherein each roller of the plurality of rollers is a member of a roller group, each roller group includes at least two rollers, rollers in a particular roller group are physically located closer to each other than to rollers in other roller groups, and at least two rollers pinch a portion of the pumping tube segment against the curved surface through a full rotation of the central rotor.
 2. The peristaltic pump according to claim 1, wherein each roller group includes three rollers.
 3. The peristaltic pump according to claim 1, wherein the plurality of rollers is distributed evenly around the circumference of the central rotor with an angular spacing of A degrees, and an angular extent of the curved surface is greater than or equal to two times A.
 4. A peristaltic pump that reduces electrical current flowing through a pumping tube segment, comprising: a central rotor mounted on a central rotation axis; a shoe with a curved surface facing toward the central rotor and having a length of the curved surface measured along the curved surface in a circumferential direction; and a plurality of rollers mounted along a circumference of the central rotor, wherein a pumping tube is positioned between the central rotor and the shoe, a pinch point on the pumping tube is defined between any roller pressing radially away from the central rotation axis against the shoe, and the curved surface of the shoe includes one or more protrusions toward the central rotor, such that pressure on the pumping tube segment between a roller and the protrusion is greater than pressure on the pumping tube segment at any other location.
 5. The peristaltic pump according to claim 4, wherein the curved surface includes two protrusions that increase the pressure on the pumping tube segment at two different locations.
 6. The peristaltic pump according to claim 4, further comprising: a biasing mechanism that exerts a force on the shoe in a direction toward the central rotor.
 7. The peristaltic pump according to claim 6, wherein the biasing mechanism includes a motor that receives control signals that modulate force applied by the motor to the shoe.
 8. The peristaltic pump according to claim 4, wherein the central rotor is pivotally mounted on a rotation axis, and a biasing mechanism exerts a force on the rotation axis in a direction toward the shoe to press the central rotor toward the curved surface of the shoe.
 9. The peristaltic pump according to claim 4, wherein the one or more protrusions include a movable plunger that extends out of the curved surface of the shoe.
 10. The peristaltic pump according to claim 9, further comprising: an opening in the curved surface through which the plunger extends out of the curved surface.
 11. The peristaltic pump according to claim 9, wherein the plunger is urged toward the central rotor by a biasing mechanism.
 12. The peristaltic pump according to claim 11, wherein the biasing mechanism includes a passive spring.
 13. The peristaltic pump according to claim 11, wherein the biasing mechanism includes a motor that is controlled by electrical signals and exerts a force with a magnitude that is based on the electrical signals.
 14. The peristaltic pump according to claim 9, wherein the shoe includes two plungers extending from the curved surface at two different locations.
 15. A method of pumping a conductive fluid while reducing electrical current flowing through the conductive fluid, the method comprising: providing a fluid pump; pumping the conductive fluid with the fluid pump; detecting a presence of the electrical current in the conductive fluid during the pumping; measuring a magnitude of the detected electrical current; comparing the measured magnitude of the electrical current against a predetermined threshold value; and in response to exceeding the threshold value, modifying the pumping of the fluid pump to reduce the electrical current flowing through the conductive fluid.
 16. The method according to claim 15, wherein the modifying the pumping of the fluid pump includes stopping the fluid pump in a state where at least two rollers press on a pumping tube segment against a pump shoe.
 17. The method according to claim 15, wherein the modifying the pumping of the fluid pump includes rotating a rotor forward or backward until at least one roller is positioned directly against a protrusion on a curved surface of a pump shoe.
 18. The method according to claim 15, wherein the modifying the pumping of the fluid pump includes increasing pressure between rollers and a pump shoe.
 19. The method according to claim 18, wherein the increasing the pressure includes at least one of using a first biasing mechanism to increase a force on a central axis of a rotor in a direction toward the pump shoe, and using a second biasing mechanism to increase a force on the pump shoe in a direction toward the central axis of the rotor.
 20. The method according to claim 15, wherein the fluid pump includes a peristaltic pump with a central rotor, a plurality of roller groups each including two or more rollers attached to the central rotor, a shoe with a curved surface that is disposed adjacent to the central rotor, and a pumping tube segment positioned between the central rotor and the curved surface, rollers in a same one of the roller groups are physically located closer to each other than to rollers in other ones of the roller groups, and at least two rollers included in one or more of the roller groups pinch respective portions of the pumping tube segment against the curved surface through a full rotation of the central rotor. 